The present invention generally relates to close-up image capture, and in particular to fill flash, close-up image capture.
The pervasive use and availability of cameras provides commercial advantage to cameras having improved performance and reduced cost. Camera costs can be reduced in the area of imaging optics, but at the cost of optical performance. For example, limiting near-field focusing capability can reduce manufacturing costs, but at the cost of creating blurry images of objects located at less than a nominal minimum focus distance from the camera. Thus, it would be advantageous to improve the near-field focusing qualities of cameras having less expensive, fixed focal length optics by substantially reducing the image blurriness of such objects.
Accordingly, one form of the present invention provides a method for image capture at less than a nominal minimum focus distance of a camera, comprising the steps of selecting a close up operational mode for the camera, initiating image capture through a variable aperture at a first aperture size, collecting a predetermined amount of ambient scene light during image capture, initiating closing of the variable aperture, and illuminating a flash unit during closing of the variable aperture at a predetermined restricted second aperture size corresponding to the close up operational mode.
The step of selecting may include determining whether an object to be photographed is located at less than a nominal minimum focus distance of the camera and also whether an object to be photographed is located within one of a plurality of ranges less than the nominal minimum focus distance. The step of illuminating may include using a separate predetermined restricted second aperture size corresponding to each of the plurality of ranges. The step of collecting may include using a separate predetermined amount of ambient scene light corresponding to each of the plurality of ranges. The step of determining may include performing a range finding function with the camera.
The step of collecting light may be performed with the variable aperture at a maximum aperture size. The step of illuminating may include detecting the predetermined restricted aperture size.
Another form of the present invention provides a camera, comprising an image capture system having a nominal minimum focus distance including a variable aperture and an exposure control system operatively coupled to the image capture system and adapted to use a fill flash function to capture images at less than the nominal minimum focus distance.
The exposure control may be adapted to collect a predetermined amount of ambient scene light during image capture, to initiate closing of the variable aperture, and illuminate a flash unit during closing of the variable aperture at a predetermined restricted aperture size. The variable aperture may use a maximum aperture size for collecting the predetermined amount of ambient scene light.
The exposure control system may include a ranging system adapted to determine whether an object to be photographed is located at less than a nominal minimum focus distance of the camera or whether an object to be photographed is located within one of a plurality of ranges less than the nominal minimum focus distance. The exposure control system may be adapted to illuminate the flash unit at a different predetermined restricted second aperture size corresponding to each of the plurality of ranges. The exposure control system may be adapted to collect a separate predetermined amount of ambient scene light corresponding to each of the plurality of ranges.
The image capture system may include a detector operatively connected to the exposure control system and adapted for sensing the predetermined restricted aperture size of the variable aperture. The variable aperture is a scanning aperture shutter.
Yet another form of the present invention provides a camera for capturing images at less than a nominal minimum focus distance, comprising an image capture system having a nominal minimum focus distance including a variable aperture; and an exposure control system operatively coupled to the image capture system and including a photocell adapted to sense ambient scene light during image capture. The exposure control is adapted to perform image capture with ambient light at a first aperture size, sense a predetermined amount of ambient scene light during image capture, initiate closing of the variable aperture, and illuminate a flash unit during closing of the variable aperture at a predetermined restricted second aperture size.
The may include a ranging system adapted to determine whether an object to be photographed is located within one of a plurality of ranges less than the nominal minimum focus distance, wherein the exposure control system is adapted to illuminate the flash unit at a different predetermined restricted second aperture size and to collect a separate predetermined amount of ambient scene light corresponding to each of the plurality of ranges.